Pig iron is the direct product of smelting iron ore, coke, and limestone in a blast furnace. It serves as the basic raw material for producing other forms of iron and steel, such as cast iron and wrought iron, through further refining processes, with a high carbon content (typically 3.5% to 4.5%) and other impurities.

A. wrought iron: Wrought iron is a purer form of iron with very low carbon content (less than 0.08%), known for its malleability. It is produced by further refining pig iron, not directly from the blast furnace.

B. cast iron: Cast iron is also an alloy derived from pig iron, usually made by re-melting pig iron with scrap iron and coke in a cupola or electric furnace. It typically has a lower carbon content than pig iron but a higher one than steel (2-3.5%), and is harder than pig iron but more brittle than wrought iron or steel.

D. carbon steel: Steel is an alloy made by significantly reducing the carbon content and removing impurities from pig iron in a separate steel-making process. It has a carbon content typically between 0.02% and 2.1% and has different properties from pig iron.